Beta-2 Agonists

What are Beta-2 Agonists?

Beta-2 agonists are a class of substances that act as ‘bronchodilators’. This means that they relax the smooth muscles that surround the lungs, and cause dilation of the vessels (bronchi), permitting more air to enter the lungs. Beta-2 agonists are often prescribed for the treatment of asthma, which is characterised by a constriction of the airways.

Beta-2 agonists are most commonly administered to the lungs using an inhaler, although they can also be injected or swallowed in tablet or syrup form.

What do they do to your body?

It is argued that athletic performance can be enhanced when beta-2 agonists are inhaled, as the widening of the bronchi increases the amount of oxygen that enters the lungs. In large doses, beta-2 agonists may also act as an anabolic agent, promoting weight gain in the form of muscle, as well as reducing body fat percentage and accelerating recovery rates.

Effects of Beta-2 Agonists

As well as acting on the muscles surrounding the lungs, beta-2 agonists also affect the heart and cardiac system. Side effects can include; tachycardia (rapid beating of the heart), palpitations (abnormal or irregular beating of the heart), headaches, tremors and anxiety.


Clenbuterol is a type of beta-2 agonist that is used in some countries as an asthma medication.

In animals, Clenbuterol has been shown to have anabolic activity and it is given to cows by farmers in China and Mexico. This is due to its thermogenic properties that trigger a breakdown of fat cells and an increase in muscle bulk.

It is also believed that Clenbuterol is used by athletes as an aid to weight loss. Accordingly, Clenbuterol is also a Prohibited Substance under the WADA Prohibited List and, therefore the Tennis Anti-Doping Programme, and so players who wish to use it for valid therapeutic reasons will need to have a valid TUE.

It has been reported that meat originating in China and Mexico for human consumption may be contaminated with Clenbuterol. When eaten in sufficient quantities, this contaminated meat has been known to result in a positive anti-doping test for Clenbuterol.

WADA is working with the governments of those countries responsible for giving their livestock Clenbuterol to address this matter. In the meantime, however, the ITF recommends that, where possible, National Associations seek assurances from suppliers that all meat provided to players in the official tournament hotel(s) and restaurant(s) is free from contamination.

The ITF is also recommending that all players participating in its tournaments:

1. Avoid eating meat in Mexico and China where possible.

2. In those countries, dine at the official or approved hotel(s) or restaurant(s).

3. If dining at non-official or non-approved locations, do so in large groups.

For further information and for news updates please visit the WADA website.